Thermostatic fuel control for heaters



H. C. LiTTLE THERMOSTATIC FUEL CONTROLv FOR HEATERS Aug. 10, 1943.

Filed April 2, 1940 INVENTOR Patented Aug. 10, 1,943 l uruTao STATESPATENT ol-Flca muy c. Lime, stemmi, cam. Application April 2, 1940,serial No. 321,454

2 claims (ci. 12e-11e) The invention relates to air circulating heatersand more particularly to a thermostatic fuel control for Such heaters.

An object of the present invention isto provide a thermostatic controlofthe character described which will operate as a safety device in anair circulating heater to limit the maximum temperature and which isresponsive to the temperature in the warm air passage of the heater andmay be incorporated into Ythe heater as a unitary part thereof.

Another object of the invention is to provide a thermostaticallycontrolled safety device of the character described which will be simpleand positive and foolproof in its operation and which will beconstructed of a minimum number of simply formed rugged and inexpensiveparts.v

A further object of the invention is to provide a control of thecharacter above which will subject the thermostatic element to a minimumstress when heated and which will provide for the closing off of thefuel supply to the burner should the thermostatic element become broken.

Yet another object of the invention is to provide a thermostatic controlof the character. described which may be readily dismantled forinspection, cleaning, repair or replacement of any of the operatingparts of the control.

Still a further object of the invention is to provide a control of thecharacter described which may be particularly designed for use in theoil line of an oil burner and which will have the final control of theoil flow to the burner and which may nevertheless be used in conjunctionwith and without interfering with the operation of an automatic oatcontrol oil valve in the oil flow line to the burner.

The invention possesses other objects and features of advantage, some ofwhich, with the foregoing, will be set forth in the followingdescription of the preferred form of the invention which is illustratedin the drawing accompanying and forming part of the specification. It isto be understood, however, that variations in the showing made by thesaid drawing and description may Vbe adopted within the scope of theinvention as portion of the view being turned from the top part oftheview. e

Figure 3 is a plan view of the control means illustrated inFigure 2.

Figure 4 is a vertical sectional view of a p0rtion of the upper end ofthe control means taken substantially at right angles tothe plane ofline 4-4 of Figure 3.

I'he thermostatic fuel control of the present invention is particularlyadapted for use with an air circulating heater such as for example, theoor furnace illustrated in the accompanying drawing. In this type ofheater there is provided a vertical warm air passage extending alongsideof the combustion casing of the heater and which is vented into the roomor other space -to be heated. 'I'he combustion casing is customarilyprovided with al burner at its lower end for heating the casing and afuel conduit leading to the burner. In accordance with the presentinvention a valve means is provided in this conduit and a thermostatmeans is mounted in the warm air passage and is operatively connected tothe valve and is so designed as to be responsive to an abnormally highoperating temperature in said passage to close the valve. Under ordinarycircumstances ofoperation with the air vpassages of the happens that arug or other Objectis placed'over the air discharge passage into theroom in such a manner as to partially or fully obstructl the air flowand in the case of the ordinary space heater it is not infrequent that agarmentor other object be placed on the heater for warming or drying. Ineither of these instances the air is confined in the passages of theheater anda dangerous rise in temperature o'f the heater is likely totake place. Even where the air passagesare not obstructed a dangerousoverloading of the unit may occur by reason of an abnormally great flowof fuel to the burner. as maybe caused by a failure of the fuel metervalve usually used in the line or by reason of causes external to theheater itself. In any of these cases the thermostatic control of thepresent invention operates to reduce,

or entirely close ofi.' the ow of fuel to the burner imtil the cause ofthe overloading is removed. i With reference more specifically to theaccompanylng drawing, the thermostatic control has been illustrated inconjunction with a. floor furnace I I of more or less standard designincluding a combustion casing I2, an outer casing I3 and intermediatelypositioned wallsA I4 which divide the space between the combustioncasing I2 and the outer casing I3 into vertical air passages I6 and I1adapted to convey the air into and out of thel heater. A top grill I8 ismounted across the upper end of the casing I3 so as to permit entry anddischarge of air into and from passages I6 and I1. As here shown, thewall I Il extends downwardly from an intermediate portion of the grillI8 to adjacent the lower end of the heater casing I2 and cool air isdrawn downwardly into the passage I8 defined between the wall I d andthe casing I3 to displace air which is heated and which rises in thepassage I 1 located between wall Id and the heater casing I2. Thepassage i1 extends upwardly alongslde of the .heater casing andregisters with the mid portion of the grill I8. In the case of a iioorfurnace as is here shown, the outer casing I3 is set in an openingformed in the iioor I9 of a room so that the several parts abovedescribed depend from the oor level. A uel burner 2i is mounted at thebottom of the casing I2 and discharges its products of combustion intothe casing for heating the latter, and a iiue 22 is here connectedadjacent the bottom of the casing I2 for discharging the spent productsinto a stack. Fuel is conducted to the burner from a metering valve 23by way of connected conduits 24 and 26 and is conducted to the meteringvalve 23 from a source by way of a conduit 21.

As above described, a fuel regulating valve 28 is mounted in the fuelpassage leading to the burner and a thermostatic means 29 is mounted inthe warm air passage I1 and the same is operatively connected to thevalve and is responsive to increasing temperatures in the passage tothrottle down the valve 28. In the present instance the valve 28 iscontained within a valve body 3I connected to the conduits 24 and 26. Avalve seat 32 is provided in the form of a removable plug threaded intothe lower end of the body 3I and the valve 28 is a needle type valvewhich moves downwardly into an opening 33 provided in the member 32 forsealing off the fuel flow. A tube 34 is threaded into the upper end 36of the valve body and extends vertically therefrom into the air passageI1 and is arranged in longitudinal alignment with the movement of thevalve 28. A bracket 31 is secured to the upper end 38 of the tube and isin turn provided with a skirt portion 39 adapted for connection to theside wall I4 of the heater. Preferably, the tube 34 is of a lengthsufticient to extend from adjacent the bottom of the burner to adjacentthe top of the passage I1. A valve stem or rod 4I is secured to orformed integrally with the valve 28 and extends upwardly through theinterior of the tube and out of the upper end of the tube, whereby theupper end 42 of the stem projects upwardly from the upper end 38 of thetube within the confines of the bracket 31. The bracket in its presentform is of generally U-shaped construction secured adjacent its centerto the upper end 38 of the tube as by means of nuts 43 and 44 andincludes a pair of transversely spaced sides 46 and 41. The thermostaticelement of the preferred form of the invention consists of an elongatedstrip 48 of bi-metal which is here supported in the bracket by extensionof opposite ends 49 and I of the strip through slots 52 and 53 in thesides 46 and 41 of the bracket. Preferably,

some means such as the cotter keys 54 and 56 here shown, are 'providedfor preventing a transverse movement of the strip relative to thebracket out of asupported position.

' As will be best seen in Figures 2, 3 and 4, the strip 48 is mountedacross the longitudinal axis of the rodin oifest relation thereto and ishere connected to the rod by means of a yoke 51 embracing the strip andextending laterally across the axis of the rod 4I and formed withthreaded openings 58 and 59 secured on the threaded upper end 42 of therod. A cap nut 5I is preferably provided over the upper end of the rod.In accordance with the present arrangement, the strip 48 in coolcondition extends substantially straight across the bracket and thelength of the stein il is such that in the cool position of the strip,the rod and valve is supported in an elevated open position Aof thevalve, as illustrated in Figure 2. The bi-metal characteristics of thisstrip are such that upon being heated the strip will bow downwardlyso asto permit a gravitation and lowering of the rod and stern towards aseated position of `the valve and at an abnormally high temperature thevalve will be fully closed. By reason of the vertical positioning andalignment of the several parts, the valve and rod will normally tend togravitate to a closed position of the valve and hence the thermostaticstrip is not called upon for any substantial actuating force when heatedto close the valve, Also, should the strip fail in its operation as byreason of breakage or failure to return to a straight position afterbeing overheated, the valve will close and remain closed until thedefect is corrected.

It will be clear that one of the functions of the tube 34 is to act as avertical guide for the valve stem and in addition, where oil fuel isused, the upper end of the tube is left open to the atmosphere so as toprovide a vent for any oil vapor formed in the oil line at or adjacentto the valve body 3 I.

The apparatus depicted in the accompanying d'awing has been particularlydesigned for use with a burner using oil as its fuel. In such case it ispreferable that the metering valve 23 be one that is float controlled,that is a valve which is constantly lled to a predetermined level withoil by means Aof a float controlled valve. In such a case it isdesirable as here shown, to locate the safety valve 28 in the linebetween the oat control valve 23 and the oil burner 2|, so that uponclosing of the safety valve 28, a minimum amount of oil will beavailable for flowing to the cil burner.

One of the advantages of the construction illustrated in the preferredform of the invention, is that the fuel flow is gradually throttled downwith increasing temperatures so as to maintain the operation of theheaterA at a safe temperature. The location of the safety valve betweenthe float control valve 23 and the oil burner gives the safety valve 28the last and final control of the oil input into the burner, andregardless of the setting of the rate of ilow of oil cut of the iioatvalve 23, the oil flow can be reduced or entirely shut off by the safetyvalve 28.

In accordance with the present invention it is extremely desirable thatthe thermostatic element be responsive to the temperature of the air inthe hot air discharge passage of the heater and so near as possible beresponsive'only to the temperature of `such air and not to thetemperature ofthe heated walls of the heater. I have found that the mosteffective control is obtained by depending upon the increasingtemperature of the air in the hot air discharge passage rather than theincreasing temperature of any of the metal parts of the heater. For thisreason I prefer to mount the thermostatic element 29 adjacent the top ofthe hot air discharge passage in furtherest removed position from theheater casing I2 so that the heat received by the thermostatic elementby radiation from the heater casing I2, will be reduced to a minimum.Thus the mounting of the thermostatic element directly in the airpassage and more particularly at the upper discharge end of the airpassage forms an important feature of the present invention.

As will be understood, other forms of thermostatic devices diilerentfrom the specic bi-metal strip herein illustrated, may be used.,

I claim:

1. In combination with a. floor furnace, an air circulating heaterincluding a combustion casing and exteriorly spaced walls defining avertical warm air passage alongside of said casing and a iiuid fuelburner mounted at the bottom of said casing to heat the same and havinga fuel inlet conduit underlying said passage, a thermostaticallyoperated valve unit comprising a valve body adapted for connection tosaid conduit at a position under said passage, a valve mounted forvertical reciprocation in said body and closing the passage. throughsaid body in its lower` position, a tube `connected to said valve bodyand extending upwardly therefrom in alignment with the movement of saidvalve, a valve stem ex tending vertically through said tube, a bimetalstrip supported by the upper end of said tube and connected to saidsternv for normally supporting the latter in an elevated open positionof said valve and/being responsive to increasing temperature in saidpassage to permit a gravitation of` said stem and valve towards closedposition of said valve, said tube being open at its upper end to permitdischarge of oil vapor.

2. In combination with a. floor furnace, an air circulating heaterincluding a combustion casing and exteriorly spaced walls defining avertical warm air passage alongside and above said casing andcommunicating with a delivery opening at the top of the heater, saidheater also having a fuel burner and a fuel inlet conduit located at thebottom of the casing. a valve comprising a body operatively connected tosaid conduit and positioned adjacent said burner, a. tube-connected toand extending upwardly from said body to adjacent said delivery openingand being open to permit discharge of oil vapor therefrom, a valvemember mounted in said tube and body for closing the passage through thevalve body, a thermostat at the upper end of said heater passagepositioned in the normal and direct vertical path of the heated airdischarging through such' passage to said delivery opening, and meansconnecting said valve member and thermostat sol that said valve memberwill move to close said valve passage in response to an increase intemperature in said heater passage.

HARRY C. LITI'LE.

